Generally, in a closed refrigeration system, high pressure gaseous refrigerant discharged from the compressor is condensed to a high pressure liquid. As this high pressure, subcooled liquid refrigerant passes through the system capillary, the temperature drops, typically from 115.degree. to 45.degree. F., while the pressure drops from 300 PSIG to 76 PSIG. In the process of this cooling, some saturated vapor forms and is present in the line leading to the evaporator. This gas must pass through the evaporator along with the liquid which is in the process of evaporation as it picks up heat from the evaporator surface.
Ideally, in a system employing Freon 22 having a pressure and temperature of 76 PSIG and 45.degree. F. respectively, at the entrance to the evaporator the pressure and temperature would be the same at the evaporator exit. However, the presence of gaseous refrigerant at the evaporator entrance as opposed to pure liquid refrigerant increases or results in a pressure drop across the evaporator. To overcome this pressure drop, the systems and more particularly the evaporator are designed to accommodate the presence of some gas and the resulting pressure drop. This is generally accomplished by increasing the effective length or inside diameter of the evaporator tubing which results in the use of extra material and, accordingly, adding cost to the system.